it seems that句型转换的问题

Question

1、It seems that she was here last week.
——She seems to HAVE BEEN here last week.
2、 It seemed that she knew everyone there-
——She seemed to KNOW everyone there.

我想知道转换后第一句为什么用have been，第二句为什么用know。
it seems to be后可接名词性从句吗？

Answer 1

1. seem to do sth中，seem后面加的是不定式的一般形式；
而seem to have done sth中，seem后面加的是不定式的完成形式。
后者表示不定式的动作发生在seem动作之前。

2. 第一句变化中，seems为一般现在时，即seem发生在现在，而was here为一般过去时，发生在过去。
也就是说不定式to be here发生在seem之前，所以使用其完成形式，即变成了：seems to have been here；
而第二句变化中，seemed和knew都是用过去式，表明这两个动作同时发生，所以只需要用seem to do sth即可。

3. It seems to be + 表语 结构中，to be经常可以省略，尤其是加表语从句时，此时一般没有to be.
所以It seems后面可以加名词性从句，it seems to be后面不加。
其表语从句一般由that，as if或as though引导。
如：It seems that you are tired. 看起来你似乎累了。
It seems as if/though it is going to rain. 看起来似乎要下雨了。

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参考资料：英语牛人团

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Answer 2

因为第二句的seem用了过去时.

Answer 3

第二句的seem用了过去时.